If John Adams' good health and productivity persist as long as that of the late Elliott Carter — whose mantle he has assumed as the most widely performed and respected living American classical composer — we may expect a steady stream of music to issue from his pen for at least three more decades. And that's a hopeful omen for a cultural subspecies badly in need of avatars.

Arguably no classical composer now active in the U.S. has produced so varied or impressive a catalog of works over so long a career as the New England-born, Northern California-based Adams.

His output is getting a thorough exploration by classical musicians and organizations worldwide this season now that he's turned 70 (Feb. 15 was the actual date).

The San Francisco Symphony, Los Angeles Philharmonic, Berlin Philharmonic, Royal Concertgebouw Orchestra and Lyons National Orchestra in France are among the major orchestras sounding anniversary fanfares, sometimes with the composer himself conducting. The global festival finale will be the world premiere of his new opera "Girls of the Golden West" by the San Francisco Opera, in November.

Ravinia has jumped aboard the anniversary bandwagon with an Adams mini-festival of its own this month and next (see sidebar of events).

Leading off a tasting menu of Adamsiana for chamber ensemble and instrumentalists will be one of his key early orchestral works, "Harmonielehre" ("Book of Harmony," 1985), to be performed on July 25 by the Chicago Symphony Orchestra under Kent Nagano, one of today's most prominent advocates of Adams' music. Adams says he hopes to drop in for one or more events if he can tear himself away from rehearsals for the new opera out on the West Coast.

I spoke to the composer by telephone in early July, just days after he finished writing "Girls of the Golden West," which is based on true stories from the mining camps and saloons of the California Gold Rush of 1850, with libretto and production by his longtime collaborator, director Peter Sellars.

Adams sounded as wryly observant as ever, as he reflected on a variety of matters cultural from the remote cabin in the Sierras that has been his creative retreat for some 40 years. The pine-shrouded shack lies only a few miles from where events depicted in his latest opera actually took place. His primary residence is the home in Berkeley he has long shared with his wife, photographer Deborah O'Grady. Their son, Samuel Adams, is one of the CSO's current composers in residence.

He was coming off the high of participating in six months of virtually nonstop anniversary activity, including conducting his opera "Doctor Atomic" at a concert performance in London in April, and the Dutch premiere of his Saxophone Concerto in Amsterdam in May, part of a multi-pronged celebration "The World According to Adams."

At the same time he wondered with bemusement why people make a "strange, fetishistic" fuss over composers when they reach big birthday anniversaries, he praised the performances his music has been receiving as "universally wonderful."

Even so, the fact that not all of those performances played to packed houses may say something about where classical music rates on the totem of today's culture, Adams observed.

"It can be a challenge to fill those enormous halls with an entire program of just my music," he said. "I was reminded that classical music is what people say it is, largely music of the past. It takes great time and effort to write music that might have a chance of entering the repertory, eventually."

Of similar concern is what he perceives as mounting classical music illiteracy in American society.

"One thing that disturbs me is that the friends I have dinner with — people who bear the same intellectual, social and political interests as I — don't listen to my music. Very few of them even listen to Beethoven. They listen to — I don't know — James Taylor or the Gipsy Kings. I realize I travel in a small cultural arena."

Is the arena getting smaller?

"I don't know," Adams replied. "I do know that it's a much better time for composers than when I was in my 20s. There's much more support now for commissioning new work. And there are all kinds of ensembles such as ICE, and Eighth Blackbird and various groups in L.A. dedicated to keeping contemporary composers in front of the public."

Not that he has anything to complain about in that regard. Virtually every piece Adams has written has been recorded, several times over in certain cases. So ubiquitous are performances of his music, in fact, that he can live comfortably off his royalties, he admitted: "I'm very, very lucky, and a rare case."

The composer also can take pride in the fact that his music has been championed by some of today's leading conductors, including Nagano, Esa-Pekka Salonen, Simon Rattle, Michael Tilson Thomas, David Robertson, Gustavo Dudamel and Edo de Waart.

"What attracts many of us to John's music is that it is masterfully written from a technical standpoint," said Nagano, the Berkeley-born music director of the Montreal Symphony Orchestra, who will be making his Ravinia debut with next week's CSO performance of "Harmonielehre." "The orchestration feels very organic, the dimensions naturally balanced."

"Harmonielehre" is the latest in a series of big local Adams premieres at Ravinia that includes the oratorio "El Nino" (heard here in 2003) and the passion play "The Gospel According to the Other Mary" (2013).

Nagano said he regards "Harmonielehre" as watershed Adams, an expansive orchestral canvas that "ingeniously ties together musical time and harmony in a different way, in which repetition becomes a process divorced from architecture."

I asked Nagano what he believes are the key elements that give Adams' output as a whole importance and durability.

"One thing that impresses many of us musicians is that John has never stopped growing as a composer," he replied. "The same voice can be traced throughout his development, from his early music to the present. The music makes an initial impression that stays with you for a long period of time. That is one mark of a composer's genius."

Listeners unfamiliar with Adams' music would call him a minimalist, but in fact his works of recent decades reveal a complexity and depth far removed from the simple pulsating patterns and repeating rhythms of his early pieces.

Certainly he has been unafraid to tackle timely political and ethical issues. His operatic subjects have included an American president ("Nixon in China"),the 1985 terrorist hijacking of the Achille Lauro cruise ship ("The Death of Klinghoffer") and the creation of the atomic bomb ("Doctor Atomic"). With "Girls of the Golden West" he and Sellars present a far more realistic slice of Gold Rush life than what's depicted in the spaghetti western by Puccini whose title the new opera alludes to.

Adams remains close to all his musical offspring, he said, even pieces such as the orchestral "My Father Knew Charles Ives" and "Naive and Sentimental Music" that have yet to catch on with audiences. "I can't say I have favorites, but I have pieces that, whenever I return to them, I'm tickled. That's especially true of 'Nixon in China.'"

Another thing that tickles Adams is listener feedback. "I'm profoundly affected when someone takes the time to write a letter, or someone else comes up to me in the supermarket to say that a piece of mine really moved them," he said. "It's what it's all about for a composer. If my music has value, it's because it makes people feel something."

He is too intensely focused on the music he's writing at present to predict, or much care about, how music historians will rate him among classical composers of the late 20th and early 21st centuries. Producing music that matters is what he's mostly concerned about, he said.

"I have some role models — Beethoven, Thomas Mann, Matisse — of whom you can say their best work came in their early, middle and late periods. That's my goal as well. I'm very proud of my early pieces and realize that, at the moment, those remain the most popular. But I hope that the work I do now — and over the next 10-15 years, if I'm fortunate enough to continue that long — will be perceived as just as good."

Adams events at Ravinia

• July 25, "Harmonielehre." The composer's early masterpiece will receive its festival debut by the Chicago Symphony Orchestra led by Kent Nagano. Also on the program is Beethoven's Piano Concerto No. 5 ("Emperor"), with Nicolai Lugansky as soloist.

• Aug. 16, "Shaker Loops." Members of Chicago's Lincoln Trio will be the core of a performance of Adams' 1978 septet,which was inspired by the repetitive dance movements of the Shakers.

• Aug. 17, Chamber Symphony and "Common Tones in Simple Time." Middle and early Adams share a program by the instrumental ensemble The Knights.

• Aug. 24, "Roll Over Beethoven" and "Hallelujah Junction." Twin sisters Christina and Michelle Naughton perform Adams' hypnotically pulsing pieces for two pianos as part of a Bennett Gordon Hall concert of duo and four-hand keyboard works by Mendelssohn, Mozart, Chopin, Debussy and Adams.

• Aug. 30, "Road Movies." There's a swing component to Adams' dynamic duo, which violinist Chad Hoopes and pianist David Fung will perform along with mainstream fare by Mozart and Beethoven.